This invention relates to human operated machines in which unwanted dynamics or vibrations are reduced. Human operated (or tele-operated) machines such as cranes are difficult to control because motion of the crane will usually result in vibration or swing of a payload supported by the crane. An example is an overhead crane which traverses a track supporting a load on a flexible member such as wire rope. The operator, using a pendant controller, causes the crane to move by energizing electric motors. Once the change in position occurs, the operator must wait until the swing oscillations decay before proceeding to the next operation. Small moves exacerbate the situation because the amplitude of the swing of the payload may be nearly equal to the total move distance. For example, a four inch move at the location of the crane hoist would result in a nearly four inch oscillation at the load. If several small moves are required, the time required for the oscillations to decay from each move will decrease overall efficiency of the operation. The elimination or reduction in load oscillation for small position adjustments (or moves) will therefore increase the speed and efficiency of crane operation.
It is known to use vibration reducing algorithms in a crane context. The known technology, however, does not suggest incremental moves with reduced vibration and the algorithms lack robustness with respect to errors in system parameters such as natural frequency and damping ratio.